| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical pickup device that enables stable track servo as well as stable information recording/reproduction. SOLUTION: Assuming that the pupil diameter of an objective lens 18 is (a) and that the range of taking in the intensity which becomes 1/e2 of a laser beam 10 entering the objective lens 18 is w, a value a/w in the tangential direction of the track of an information recording medium 1 is set smaller than a/w in the radial direction of the recording medium. A change in the spot in the tangential direction is thereby reduced. As to unactuated servo due to change in the spot diameter in the radial direction, a track error signal amplitude is measured in accordance with the position of the recording layer 2 of the recording medium 1. By getting the optimum track gain from the result of this measurement and by actuating by the track gain, a stable servo signal and a recording/reproducing signal are obtained. |
